In a laser machining machine for moving a machining head, the length of an optical propagation path for communicating a laser oscillator and light gathering means with each other varies depending on the move position of the machining head. Thus, to maintain the optical path length fitted for the divergence characteristic of laser, it is necessary to lengthen or shorten the optical path length of a laser beam at some part on the propagation path for always keeping the propagation path from the laser oscillator to the light gathering means in the optical length.
Hitherto, a laser machining machine having an optical path length control mechanism for moving a machining head as shown in FIG. 10 has been available. In FIG. 10, a laser beam 11 output from an oscillator 3 passes through a path of reflecting mirrors a1 to a7 and arrives at a machining head 2.
Here, as shown in FIG. 10, if the machining head 2 is at a position above the left end of a machining table 1, an optical path length adjustment block 6 is positioned at a lower end of an optical path length control section 7 and the length from the oscillator 3 to the machining head 2 at this time is adopted as the reference length.
A control unit 4A calculates so that the propagation path length becomes the reference length regardless of what position the machining head 2 moves to, and sends a command to an amplifier SAu for driving the optical path length adjustment block 6. Then, a motor SVu is driven and the optical path length adjustment block 6 moves for keeping the propagation path in the reference length.
For example, if the machining head 2 moves to a position shown in FIG. 11, the propagation path lengthens (X+Y). Since the laser beam 11 is turned back in the optical path length control section 7, the optical path length adjustment block 6 is moved upward by a half of (X+Y).
In doing so, the propagation path length becomes the reference length.
Since the laser machining machine having the optical path length control mechanism in the related art is configured as described above, the optical path length adjustment block always moves in synchronization with the position of the machining head, whereby the propagation path length is controlled so as to become the reference length.
Thus, whenever the machining head moves, the optical path length adjustment block needs to move, and the belt for driving the optical path length adjustment block, the guide for supporting the optical path length adjustment block, and the like are worn heavily.
Particularly, to perform fine line segment machining like laser machining, acceleration and deceleration are frequently performed and thus the belt, the guide, and the like are worn still more rapidly.
Since it is necessary to always move the optical path length adjustment block, power is also consumed.
To synchronize with a move of the machining head, acceleration and deceleration at the moving time of the optical path length adjustment block need also be set to high values as acceleration and deceleration of the machining head and if acceleration and deceleration are set high, vibration is easily induced and thus rigidity of the optical path length mechanism needs to be enhanced.